Fix #7 Support multiple env vars in same string

Use non-greed regex to avoid capturing multiple env-like strings.
Keep parsing until all env-like strings are substituted.

README.rst

@@ -62,6 +62,18 @@ The environmental variable can be embedded in a larger string, too:
         'b': 2
     }
 
+More than one environmental variable can appear in a string:
+
+.. code-block:: python
+
+    yamlenv.load('''
+        a: foo ${A:-bar} ${B:-baz}
+        b: 2
+    ''') == {
+        'a': 'foo bar baz',
+        'b': 2
+    }
+
 YaML files can include other YaML files, too. E.g. if ``b.yaml``
 contains "2", then:
 

tests/test_env.py

@@ -41,6 +41,23 @@ def test_interpolate_string(self):
 b: 2
         '''), {'a': 'password', 'b': 2})
 
+    def test_interpolate_two_values(self):
+        os.environ['A'] = '1'
+        os.environ['B'] = 'foo'
+        self.assertEqual(yamlenv.load('''
+a: ${A} ${B}
+            '''), {'a': "1 foo"})
+
+    def test_interpolate_two_values_with_defaults(self):
+        self.assertEqual(yamlenv.load('''
+a: ${C:-foo} ${D:-bar}
+            '''), {'a': "foo bar"})
+
+    def test_interpolate_invalid_yaml_value(self):
+        self.assertEqual(yamlenv.load('''
+{'a': {'b': '{foo} ${C:-foo}'}}
+            '''), {'a': {'b': "{foo} foo"}})
+
     def test_interpolate_within_characters(self):
         os.environ['A'] = 'def'
         self.assertEqual(yamlenv.load('''

yamlenv/env.py

@@ -1,6 +1,7 @@
 import os
 import re
 import yaml
+import yaml.parser
 
 try:
     from collections.abc import Mapping, Sequence, Set
@@ -46,7 +47,7 @@ class EnvVar(object):
     __slots__ = ['name', 'separator', 'default', 'string']
 
     RE = re.compile(
-        r'\$\{(?P<name>[^:-]+)((?P<separator>:?)-(?P<default>.*))?\}')
+        r'\$\{(?P<name>[^:-]+?)((?P<separator>:?)-(?P<default>.*?))?\}')
 
     def __init__(self, name, separator, default, string):
         # type: (str, str, str, str) -> None
@@ -65,15 +66,19 @@ def value(self):
         # type: () -> str
         value = os.environ.get(self.name)
         if value:
-            return self.RE.sub(value, self.string)
+            return self.RE.sub(value, self.string, count=1)
         if self.allow_null_default or self.default:
-            return self.RE.sub(self.default, self.string)
+            return self.RE.sub(self.default, self.string, count=1)
         raise ValueError('Missing value and default for {}'.format(self.name))
 
     @property
-    def yaml_value(self):
+    def maybe_yaml_value(self):
         # type: () -> T.Any
-        return yaml.safe_load(self.value)
+        v = self.value
+        try:
+            return yaml.safe_load(v)
+        except yaml.parser.ParserError:
+            return v
 
     @classmethod
     def from_string(cls, s):
@@ -89,11 +94,16 @@ def from_string(cls, s):
 
 def interpolate(data):
     # type: (T.Any) -> Obj
-    for path, obj in objwalk(data):
-        e = EnvVar.from_string(obj)
-        if e is not None:
-            x = data
-            for k in path[:-1]:
-                x = x[k]
-            x[path[-1]] = e.yaml_value
+    while True:
+        more = False
+        for path, obj in objwalk(data):
+            e = EnvVar.from_string(obj)
+            if e is not None:
+                more = True
+                x = data
+                for k in path[:-1]:
+                    x = x[k]
+                x[path[-1]] = e.maybe_yaml_value
+        if not more:
+            break
     return data